1. Field of the Invention
The present invention generally relates to weapons and artillery and, more particularly, to penetrating systems and penetrating weapons that may be used, for example, to damage and destroy sheltered targets.
2. State of the Art
In military operations, targets may be generally classified as either unsheltered targets or sheltered targets. Unsheltered targets may be considered to include targets which are substantially exposed and vulnerable to a weapon or projectile fired by artillery directed at such targets. For example, people, munitions, buildings and other fighting equipment that are openly located on a battle field and substantially exposed to the weapons of an enemy attack may be considered unsheltered targets.
However, many targets including, for example, people, munitions, chemicals, and fighting equipment may be sheltered in order to protect them from an attack by various weapons. Conventionally, a shelter for a target includes a physical barrier placed between the target and the location of origin of an expected enemy weapon in an attempt to frustrate the weapon directed at the target and mitigate the damage that might otherwise be inflicted by such a weapon. In some cases targets may be heavily sheltered in an attempt to prevent any damage to a given target. In one example, one or more layers of concrete, rock, soil, or other solid material may be used in an effort to protect a desired target. Each layer may be several feet thick, depending on the level of protection desired. Sometimes these layers are referred to as “hard” layers indicating a relative amount of resistance that they will impose on an impending weapon. Generally, a layer is considered to be “hard” when it exhibits a specified level of thickness, when it is formed of a material exhibiting a specified level of hardness or some other material characteristic which significantly impedes penetration of a weapon, or when the layer exhibits a desired combination of material properties and physical thickness.
More specific examples of shelters for targets include a building, a room in a building, a bunker, a room in a bunker, or a room or a bunker located beneath a building. Considering a bunker as an example, the ceiling of a bunker may be configured as a hard layer in order to protect people, things, or a combination thereof, from non-penetrating weapons. Additionally, multiple hard layers may be used to shelter a target. Voids may be present between multiple layers for structural reasons or for purposes of trying to confuse existing weaponry designed to defeat such shelters by causing premature detonation.
In order to penetrate shelters, and particularly a hard layer (or layers) of a given shelter, a weapon configured with a penetrator system is conventionally used. The general goal of using a penetrator system is to breach the shelter, including any thick layers that may be present, and deliver the weapon to a desired location (i.e., proximate the intended target) while delaying detonation of the weapon until it is at the desired location. Thus, use of a penetrator system enables a more efficient and a more effective infliction of damage to a sheltered target and, sometimes, use of such a system is the only way of inflicting damage to certain sheltered targets.
A penetrator system is part of a weapon system which may include one or more warheads, a penetrator structure (generally referred to as a penetrator) and a sensor associated with and coupled to the penetrator. The penetrator may be configured to act as a warhead, or it may be a separate component, but generally includes a mass of relatively dense material. In general, the capability of a penetrator to penetrate a given layer of media is proportional to its sectional density, meaning its weight divided by its cross-sectional area taken along a plane substantially transverse to its intended direction of travel. The weapon system may include equipment for guiding the weapon to a target or, at least to the shelter, since, in many cases, forces associated with impact and penetration of a shelter may result in the removal of such equipment from the penetrator portion of the weapon. The sensor of a penetrator system is conventionally configured to assist in tracking the location of the penetrator as it penetrates layers of one media type or another after an initial impact of the penetrator with the shelter.
Some prior art penetrator system sensors are configured to detect an initial impact with a structure and then measure the amount of time that has lapsed subsequent the detected impact in an effort to keep track of the location of a penetrator, based on calculated or estimated velocity of the weapon, as the penetrator penetrates a shelter. These sensors are generally referred to as time-delay sensors.
Other prior art penetrator system sensors use an accelerometer to measure the deceleration of the penetrator, from the time it makes an initial impact with a layer of a shelter or structure, in an effort to track the distance that a penetrator travels after impact with an initial layer. These sensors have generally been referred to as penetration depth sensors.
Some prior art penetrator systems utilize an accelerometer to detect deceleration of relatively hard and/or thick layers in an effort to help count the layers of media, count voids between the layers of media, or count both media layers and voids.
Such prior art time-delay and penetration depth sensors, in association with other system components, provide an output signal for detonating the weapon after the penetrator system has determined that the penetrator has arrived at a desired location within the shelter based on either time of travel information, depth of penetration information, or media counting information. When the penetrator system is programmed with a time delay or penetration depth parameter, the penetrator system detonates the weapon when the programmed parameter matches the actual penetration time or penetration distance of the weapon after an impact with an initial layer. Desirably the detonation of the weapon occurs at a target site such as within a specified room of a bunker. However, in practice, any of a number of factors, such as variability in the physical or material characteristics of a given layer or the presence of other, unexpected physical components associated with a shelter, can alter the actual time required to travel from the initial point of impact with a shelter to the desired target or the perceived distance traveled by a penetrating weapon after initial impact with a layer of a shelter.
Variations in a shelter, or in a layer of a shelter, may include variations in the thickness and/or hardness of a building's (or bunker's) roof and floors, variations in the number and types of mechanical equipment within a shelter (e.g., plumbing and HVAC equipment within a building), variations in the furnishings within the shelter, or the existence of other structural features of the shelter not previously considered or anticipated. With respect to the thickness and hardness of a given shelter layer, such may not always be known due to many variables including, for example, type of media the layer is formed of (e.g., concrete, soil, or sand), thickness of each media in the layer, the age of a layer (e.g., the age of a concrete layer), soil type, moisture content of a given layer, and temperature of a layer or its surrounding environment. It is noted that, for example, frozen or compacted soil is much harder than sand and, therefore, provides a different level of resistance to penetration.
Due to the existence of such variations in a shelter, and the inability of prior art penetrator systems to account therefor, such penetrator systems may cause the weapon to prematurely detonate or to detonate late such that it does not detonate at the actual site of the intended target. More specifically, prior art systems using time-delay or penetration depth sensors can be used to accurately detonate the penetrator at a specified location (e.g., a specified room in a bunker) only if the thickness and hardness of each media from the roof to the room are known. Since the thickness and hardness of the media are conventionally not known for many constructions over a bunker, prior art time delay and penetration depth sensors cannot reliably fire a penetrator at the desired location.
Additionally, while penetrator systems have been used to detect decelerations that result from the presence of a relatively thick or hard layer, such penetrator systems cannot effectively detect layers that are thin, soft, or some combination thereof, due to the relatively low amount of deceleration experienced by the penetrating weapon when passing through such thin or soft layers. Some examples of “thin” layers include ceilings and floors in buildings that may be located over a target. Some examples of “soft” layers include layers of sand or other soft soil. Generally, a layer is too thin or too soft to detect when the deceleration of a penetrating weapon, as it passes through such a layer, cannot be discerned from electrical noise, mechanical noise, or combination of electrical and mechanical noise experienced by the sensor. For example, a penetrator system may experience mechanical noise through the vibrations induced into the penetrator system upon impact and penetration of a given layer.
Some prior art systems have utilized gain switching in an effort to detect relatively thin layers. Gain switching generally includes use of a high gain amplifier to detect low levels of deceleration by the penetrating weapon and use of a lower gain amplifier as deceleration of the penetrating weapon increases. Such gain switching may occur between a computer sampling of the penetrating weapon's deceleration. Gain switching may generally be accomplished using one or more amplifiers, one or more analog-to-digital converters, or some combination thereof.
As briefly noted above, some prior art penetrator systems have employed what may be referred to as void and layer counting methods. Generally, such penetrator systems utilize sensors in an effort to count discrete layers, voids or both, after detecting an initial impact. However, these penetrator systems cannot reliably detonate a penetrator at the intended target location since, as with other systems, they cannot reliably detect and count the thin layers of a given shelter building. If a layer is not properly detected, the penetrator system will detonate the penetrator late, at a location beyond that of the intended target. Some attempts have been made to adjust the sensor thresholds of a penetrator system so that they only detect so-called “hard” layers and effectively ignore all thin or soft layers of a shelter. However, such attempts unfortunately result in the sensor ignoring a layer that is significant to a well-timed detonation such as, for example, the ceiling of a bunker, again resulting in the detonation of the penetrating weapon at an undesired location.
Other configurations of prior art systems have included redundancy such that multiple samples of deceleration are required to verify detection of a layer and prevent early detonation of the weapon. Such redundancy systems have also been used in conjunction with time-delay and penetration depth systems.
In yet other prior art penetrator systems, attempts have been made to prevent the system from counting a single layer as more than one layer. To do so, such penetrator systems used a programmed distance, sometimes referred to as a “blanking distance,” to ignore both false layers and real layers after the penetrator system detected deceleration. In one example, a prior art penetrator system would calculate and measure the blanking distance traveled by the penetrator system based on the penetration velocity of the penetrator system at the time of its impact with a layer and the time that expired after such impact. Some other penetrator systems have also used the deceleration values and the detection of an exit of the penetrator system from a penetrated layer to help determine the blanking distance.
There is a continued desire to improve the penetrator systems used in weapons so as to increase their accuracy in determining their arrival at a desired location and thereby ensure a maximization of damage inflicted on a desired target. It would be desirable to provide such improvements through simple implementations so, for example, existing prior art systems may be updated and retrofitted in a simple and inexpensive manner.